Macrolactin A protects against LPS-induced bone loss by regulation of bone remodeling

Tianhe Zhuifeng Gao reverses inflammatory response and attenuates bone/cartilage destruction in rheumatoid arthritis via PSMC2-RUNX2-COL1A1 axis based on transcriptional regulatory network analysis and experimental validation

BACKGROUND

Tianhe Zhuifeng Gao (TZG) is an authorized Chinese patent drug with satisfying clinical efficacy, especially for RA patients with cold-dampness syndrome. However, its underlying pharmacological mechanisms remain unclear.

METHOD

Anti-arthritic effects of TZG were evaluated using an adjuvant-induced arthritis (AIA) rat model. Transcriptional regulatory network analysis based on synovial tissues obtained from AIA rats, combining with our previous analysis based on whole blood samples from RA patients with cold-dampness syndrome and co-immunoprecipitation were performed to identify involved dominant pathways, which were experimentally verified using AIA-wind-cold-dampness stimulation modified (AIA-M) animal model.

RESULTS

TZG treatment dramatically attenuated joint injury and inflammatory response in AIA rats, and PSMC2-RUNX2-COL1A1 axis, which was closely associated with bone/cartilage damage, was inferred to be one of therapeutic targets of TZG against RA. Experimentally, TZG displayed obvious pharmacological effects for alleviating the joint inflammation and destruction through reinstating the body weight, reducing the arthritis score, the limbs diameters, the levels of RF and CRP, and the inflammatory cytokines, recovering the thymus and spleen indexes, diminishing bone and cartilage destruction, as well elevating the pain thresholds of AIA-M rats. In addition, TZG markedly reversed the abnormal energy metabolism in AIA-M rats through enhancing articular temperature, daily water consumption, and regulating expression levels of energy metabolism parameters and hormones. Moreover, TZG also significantly modulated the abnormal expression levels of PSMC2, RUNX2 and COL1A1 proteins in the ankle tissues of AIA-M rats.

CONCLUSION

TZG may exert the bone protective effects in RA therapy via regulating bone and cartilage damage-associated PSMC2-RUNX2-COL1A1 axis.

Metabolic bone disorders and the promise of marine osteoactive compounds

Metabolic bone disorders and associated fragility fractures are major causes of disability and mortality worldwide and place an important financial burden on the global health systems. These disorders result from an unbalance between bone anabolic and resorptive processes and are characterized by different pathophysiological mechanisms. Drugs are available to treat bone metabolic pathologies, but they are either poorly effective or associated with undesired side effects that limit their use. The molecular mechanism underlying the most common metabolic bone disorders, and the availability, efficacy, and limitations of therapeutic options currently available are discussed here. A source for the unmet need of novel drugs to treat metabolic bone disorders is marine organisms, which produce natural osteoactive compounds of high pharmaceutical potential. In this review, we have inventoried the marine osteoactive compounds (MOCs) currently identified and spotted the groups of marine organisms with potential for MOC production. Finally, we briefly examine the availability of in vivo screening and validation tools for the study of MOCs.

Chebulinic acid alleviates LPS-induced inflammatory bone loss by targeting the crosstalk between reactive oxygen species/NFκB signaling in osteoblast cells

Chebulinic acid (CA), a plant ellagitannin derived from Triphala, is reported to exhibit both anti-inflammatory & anti-oxidant activity apart from anti-tumour property. However, its role in inflammatory bone loss conditions was unexplored. We hypothesized that CA may prevent the bone loss under inflammatory conditions induced by lipopolysaccharide (LPS) in 10-week-old male C57BL/6J mice. Micro-CT analysis and histomorphometric evaluations were carried out where it was found that CA significantly improved the bone micro-architectures by enhancing trabecular connectivity and strength of the bone. CA also increased the bone regeneration as examined by calcein labelling and ex-vivo mineralisation along with maintaining the bone serum markers. Further, CA ameliorated the reduction in osteoblast cell differentiation, proliferation and viability after LPS stimulation. DCFDA and Mitosox staining revealed that CA presented remarkable protective effects against LPS treatment by attenuating oxidative stress, both at cellular & mitochondrial levels. In addition, CA significantly decreased the production of pro-inflammatory cytokines, and down-regulated the phosphorylation of NFκB and IκBα, indicating that CA could attenuate the inflammatory impairment to primary osteoblast cells by suppressing the NFkB signalling pathway. Taken together, the protective role of CA against LPS-induced bone loss & inhibitory effect on total ROS levels hold promise as a potential novel therapeutic strategy for the inflammatory diseases in bones.

Lipopolysaccharide-Induced Bone Loss in Rodent Models: A Systematic Review and Meta-Analysis

Osteoporosis has traditionally been characterized by underlying endocrine mechanisms, though evidence indicates a role of inflammation in its pathophysiology. Lipopolysaccharide (LPS), a component of gram-negative bacteria that reside in the intestines, can be released into circulation and stimulate the immune system, upregulating bone resorption. Exogenous LPS is used in rodent models to study the effect of systemic inflammation on bone, and to date a variety of different doses, routes, and durations of LPS administration have been used. The study objective was to determine whether systemic administration of LPS induced inflammatory bone loss in rodent models. A systematic search of Medline and four other databases resulted in a total of 110 studies that met the inclusion criteria. Pooled standardized mean differences (SMDs) and corresponding 95% confidence intervals (CI) with a random-effects meta-analyses were used for bone volume fraction (BV/TV) and volumetric bone mineral density (vBMD). Heterogeneity was quantified using the I² statistic. Shorter-term (<2 weeks) and longer-term (>2 weeks) LPS interventions were analyzed separately because of intractable study design differences. BV/TV was significantly reduced in both shorter-term (SMD = -3.79%, 95% CI [-4.20, -3.38], I² 62%; p < 0.01) and longer-term (SMD = -1.50%, 95% CI [-2.00, -1.00], I² 78%; p < 0.01) studies. vBMD was also reduced in both shorter-term (SMD = -3.11%, 95% CI [-3.78, -2.44]; I² 72%; p < 0.01) and longer-term (SMD = -3.49%, 95% CI [-4.94, -2.04], I² 82%; p < 0.01) studies. In both groups, regardless of duration, LPS negatively impacted trabecular bone structure but not cortical bone structure, and an upregulation in bone resorption demonstrated by bone cell staining and serum biomarkers was reported. This suggests systemically delivered exogenous LPS in rodents is a viable model for studying inflammatory bone loss, particularly in trabecular bone. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

AP-002: A novel inhibitor of osteoclast differentiation and function without disruption of osteogenesis

AP-002 is a novel, gallium-based, anti-cancer oral compound in clinical development for cancer patients with bone metastases. We examined the effects of AP-002 on osteoclastogenesis, fusion, and osteogenesis. AP-002 exhibited a dramatic effect on osteoclast function without causing osteoclast cell death. The expression of tartrate-resistant acid phosphatase and cathepsin K mRNA levels was down-regulated in RAW264.7 cells treated with AP-002 in the presence of soluble receptor activator of NF-κB ligand. AP-002 was also found to block the fusion of osteoclasts from RAW264.7 cells. AP-002 had a similar inhibitory effect on RANKL-induced mouse primary bone marrow monocytes fusion. Human blood monocytes treated with AP-002 failed to form TRAcP/ACP5-positive cells. AP-002 caused these inhibitory effects without causing osteoclast cell death, which was in contrast to zoledronic acid controls. Furthermore, unlike zoledronic acid, AP-002 did not inhibit Rac1 activation. Gene expression analysis by microarrays showed that AP-002 significantly reverses the effects of RANKL-induced gene expression. These include several key osteoclast-differentiation/function-associated genes such as: Scinderin, OCSTAMP, Atp6v0d2, OSCAR, RhoU, Usp18, MMP9, and Trim30. The difference between AP-002 and zoledronic acid is also seen in its effects on osteogenesis. Osteoblast mineralization was promoted by AP-002 (0.1-3.0 μM), whereas zoledronic acid showed toxicity to osteoblasts at the concentration >0.5 μM, in the same dose range where it causes osteoclast cell death. Zoledronic acid therefore has no therapeutic window in its toxic effect on osteoclasts and osteoblasts. AP-002 promotes osteogenesis in this therapeutic window, while blocking osteoclast development. We therefore conclude that AP-002 has potential as a new anti-bone resorption agent, with a mechanism of action different compared with other currently marketed anti-bone resorption agents.